Apparatus and method for completing wells



Nov. zo, 1962 H. A. BOURNE, JR 3,064,733

APPARATUS AND METHOD FOR COMPLETING WELLS BKQMMZM A TTR/VEY Nov. 20,1962 H. A. BOURNE, JR

APPARATUS AND METHOD FOR COMPLETING WELLS Filed 00T'. 29, 1959 4Sheets-Sheet 2 HENRY A. BOURNE, JR.

ATTORNEY Nov. 20, 1962 H. A. BOURNE, JR

APPARATUS AND METHOD FOR COMPLETING WELLS Filed oct. 29, 1959 4 4Sheets-Sheet 3 JNVENTOA HE/vny .4.e0uHA/E, ./R.

ATTORNEY Nov. 20, 1962 H. A. BOURNE, JR 3,064,733

APPARATUS AND mamon FOR COMPLETING WELLS Filed OG.. 29, 1959 4Sheets-Sheet 4 1N V EN TOR. i HEN? Y A HOUR/VE', JR(

ATTORNEY United States Patent Ollice ,tged

3,064,733 APPARATUS AND METHOD FOR COMPLETENG WELLS Henry A. Bourne,Jr., Ponca City, kla., assigner to Continental Oil Company, Ponca City,Okla., a corporation of Delaware Fiied Get. 29, 1959, Ser. No. 849,662'8 Claims. (Cl. 15e-55) This invention relates to an improved method andapparatus for completing oil and gas Wells. This invention is acontinuation-in-part of my co-pending application, Serial No. 631,606entitled, Apparatus and Method for Completing Wells, filed December 31,1956, now abandoned.

As is well known in the art, many oil and gas wells are completed byperforating either the casing or the open well bore in the depthintervals where it is expected that oil and gas will be produced. Theperforating may be accomplished by means of bullets, shaped charges, orpunch-type perforators. A perforating gun containing the desiredperforating means is lowered through the well bore on the lower end of asuitable cable and positioned opposite the formation to be perforated.Ordinarily, the drilling mud used in drilling the well is maintained inthe well bore during the perforating operation to maintain a hydrostaticpressure in excess of the formation pressure. The drilling iiuid or mndinvariably contains solid materials which are normally used to provide alow loss of fluid from the drilling mud to the various formations. Inaddition, some muds contain solids for density control. These solidmaterials will enter the perforation during and subsequent to theperforating operation to effectively Y plug 0E the channels or holesmade by the perforating means and thus inhibit the flow of formationfluids into the well bore. Some of the plugging material may be removedunder producing conditions; but in many cases, it remains in theperforations permanently. Many drilling muds have water as a primaryconstituent, and the water is forced into the perforations underhydrostatic pressure, entering the portion of the formation surroundingeach perforation. Frequently water causes native clays in the producingformation to swell, resulting in a permanent reduction in formationpermeability near the perforation.

The plugging problem arising when drilling mud is.re tained in a well asthe well is being perforated has been recognized by those skilled in theart. Heretofore, however, the solutions to the problem which has beenadvanced involve the replacement of either all or a substantial portionof the drilling mud from the well bore, and the substitution of thedrilling mud with a more desirable perforating fluid. In the use of suchsolutions, a tubing is ordinarily run into the well bore either to thebottom of the well or to a position below the formation which is to beperforated. 'Ihe desirable perforating Huid is then forced downwardlythrough the tubing and upwardly in the aunulus between the tubing andthe well casing (or the well bore), thus displacingv the drilling mud.After the desired amount of drilling mud has been displaced, the tubingmust be removed from the well and then the perforating gun is lowered tothe desired position and red. 4It will be apparent that, with this typeof operation, a very substantial amount of the drilling mud must bedisplaced to assure that the desirable perforating fluid will occupy theentire zone which is to be perforated. The operation also involves thetime-consuming and expensive job of running and removing a completestring of tubing into the well bore prior to the actual perforatingoperation. Unless the displacing fluid in this operation has a densityequal to or in excess of that of the drilling uid, there is no assurancethat the displacing fluid will remain in place while the tubing is beingpulled and prior to the perforating process. A

The present invention contemplates a method wherein the perforating gunis lowered through the drilling mud to the desired perforating position.The drilling mud im'- mediate surrounding the perforating gun is thendisplaced by an optimum perforating fluid and subsequently thereafterthe gun is red while said perforating iluid is in position surroundingthe gun. Thus the perforating means will not force drilling mud into theperforations, and the perforations will be immediately filled with anoptimum fluid to exclude the plugging action of the usual drilling mud.As to apparatus, we contemplate a novel attachment for a perforating gunwhich functions Vto retain a supply of optimum perforating fluid withthe gun and to expel the optimum perforating fluid upwardly around thegun prior to the perforating operation, whereby the 'desir-- able benetsdescribed above will be attained.

An important object of this invention is to improve oil and gasWell-completion techniques. v

Another object of this invention is to prevent the plug@ ging ofperforations by drilling mud or materials con tained in the drilling mudduring the completion of di and gas wells. A further object of thisinvention is lto displace drilling` mud from around a perforating gunwith an optimum perforating fluid during the perforating of a well.Another object of this invention isv to displace the drill? ing mud fromaround a perforating gun by means of a minimum of equipment andmanipulations of instruments in and out of the well bore during aperforating operation. A still further object of this invention is toprovidejan attachment for a perforating gun whereby thedrillingmud maybe displaced from around the perforating gun prior to tiring the gun ina well bore. Other objects and advantages of the invention will:l beevident from the following detailed description, when read inconjunction with the accompanying drawings, which illustrate myinvention. Y t" In the drawings: FIGURE l is a vertical sectional viewthrough a por tion of a well bore having a perforating gun suspendedtherein, with a portion of the perforating gun being Vshown in sectionto illustrate details of construction. FIGURE 2 is a continuation fromthe lower end of FIGURE 1 illustrating my preferred perforating liuidplacement tool attached to the lower end of the perforatlng gun.

FiGURES 3, 4, 5, and 6 illustrate the various steps involved inpracticing the method of the present inventiorr. FIGURE 7 is a verticalsectional view through a modified perforating fluid placement tool.

FIGURE 8 is a vertical sectional view through` still another modifiedperforating fluid placement tool.

FIGURE 9 is a vertical sectional view through still another modifiedperforating uid placement tool.

Referring to the dra-wings in detail, and particularly to FIGURE l,reference character 10 designates a well bore having the usual wellcasingv 12 secured therein by means of a cement sheath, partially shownat 14, in the aunulus between the well bore 10 and the casing 12. Itwill be understood that although we have shownl the use of a well casing12, the present invention is applicable to wells completed openholewherein no casing is used through the potentially producing formations.Of course, the cement sheath 14 is merely illustrative of a typicallwell installation and is not limiting on the present inven= tion.

A perforating gun, generally designated by reference character 16, issuspended in the well casing 12 by means of a cable 1S. The cable 18 isof a type which will support the perforating gun 16, and through whichsuitable electric leads or wires (not shown) extend to provide aconduction of electric current from the surface of the well to theperforating gun 16. The upper end of the cable 1 8 is ordinarilyconnected to a suitable tiring mechanism or instrument truck (not shown)at the surface of the well for actuating the Perforatiag sun 16- Thelower end of the cable 18 is connected to the per-forating gun 16 bymeans of a suitable cable connector 20.

The perforar-ing gun 1 6 comprises a suitable tubular housing 22 havingalseries of shaped charge-type perforators 24 therein in the usualmanner. It will be understood that the shaped char-geftype perforators 24 may be replaced with any other suitable type of perforating means,such as bulletperforators (n ot shown). A fuse 26 extends lengthwisethrough the gun housing 22 and through the tiring ends of theperforators 24 to tire the perforators 214 in rapid succession. Asuitable detonator 28 is connected to the lower end of the fuse 26 andis secured in the lower end portion of the housing 22 by means of asuitable bracket` 30. The detonator 28 is electrically connected to asingle pole, double throw switch 32 and a suitable ground wire 34leading to the housing 22. A lead wirel 316 extends upwardly from thecenter pole of the switch 32 to the cable 18, and thence to the surfaceof the well, whereby the center pole of the switch 32 will be energizedwhen ay suitable electrical current is supplied from the surfaceinstallation. The switch 32 is sellred the lower end portion of thehousing 22 opposite the detonator 2,8 by a suitable bracket 38. Theswitch 32 is preferably of the toggle type, wherein the switch armprovide electrical communication between the lead 36 and the detonator28 when the lever is in its ripper position, as will be morefully'hereinafter .set forth.

A plug 40 (see also FIGURE 2) is secured in the lower end o f theperforating gun housing 22 and extends upwardly into the gun housing toa point immediately below the switch 32. It is preferred that the plug40 be sealed 1o the inner periphery of the gunY housing 22 by a suitablesealing ring 42, whereby drilling mud and the like will not leakirltothe gain housing 22 and interfere with the operation of the perforatinggun. A bore 44 extends vertically through the central portion of theplug 40 to slidingly receive a push rod 46. However, the rod 46 issealed to the walls of the bore 44 by a sealing ring 47. .The upper endof the push rod 46 is suitably shaped to contact and actuate the leverof the switch 32, and the lower end of the. pushl rod `476 extends asubstantial distance .below the plug 40. A suitable flange-type stop 48is. formed on; an intermediate -portion of the push rod 46 below thelower face 50 of the plug 40, for purposes which will behereinafter setforth. A second bore S2 extends rer-.tieally through the plug v40 toreceive suitable insulation '4 and a lead 56 rdepending from the lowerend of the switch 32. The lead $6 extends through the insulation 54,whereby a potential imposed on the lead 56 'will notbe short circuitedthrough the plug 40.

The lower end of the plug 40 is counterbored and in'- ternally threadedto receive the upper head 58 o f a lower tubular housing 60. The upperend of the head 58 is also counterbored to provide a chamber 62immediately below and in communication with the lower end face 5 0 ofthe plug 40. A series of discharge ports 64 extend through the Walls ofthe head 58 from the chamber 62 yin circumferentially spaced relation.The discharge ports 64.commu nicate with mating ports extending throughthe lower skirt portion of the plug 40, whereby cornmunicationisestablished from the chamber 62 to the annulus between the plug 40 andthe casing 12.

A plurality of vertical ports I66 extend downwardly through the head 58from the chamber 62 to communieating transversely extending ports 68.The ports 68 lin turn communicate with a centrally located passageway70. For'purposes of description, the passageway 70 may be considered asan extension of the main chamber 72 ofH theA housing 60. The push rod 46extends downwardly through the* chamber 62 and loosely through a bore 74in thehead 58 into the passageway 70, whereby the 'lower 4 end of thepush rod 46 will be exposed to the main chamber 72' of the housing 60.

An expandable packer 76 is disposed around the outer periphery of thehead 58 immediately below the lower end of the plug 40. The packer 76may be suitably secured to the lower end of the plug 40 and an upwardlyextending shoulder 78 of the housing 60 in a position directly oppositethe transverse ports 68. The packer 76 is of a size to expand and engagethe inner periphery of the well casing 12 when fluid under pressure isforced outward-ly through the transverse ports 68 into contact with thepacker.

The lead 56 extends on downwardly through .the head 58 and may beextended through one of the vertical ports `66 and then through anVL-'shaped passageway 80 to the outer periphery of the head 58 near the,lower end thereof. A suitable insulating plug 82 is secured around thelead 56 at the point where the lead emerges from the head 58 and thelead 56 will be` suitably insulated from the head 58. throughout thelength of the head. From the insulated plug 8-2, the lead 56 preferablyextends downwardly along the outside of the housing 66 to the lower endof the housing.

The main chamber 72 of the housing 60,` is of substantial length and isprovided to contain a supply of optimum perforating fluid,V as. will bemore fully hereinafter set forth. A piston 84 is reciprocably disposedin the main chamber 72 and is sealed to the inner periphery of thechamber by suitable sealing rings 86. The piston 84 has a bore 88extending vertically through the central portion thereof to slidinglyreceive a valve rod 90 which has a valve head 92 on the lower endthereof. The lower end of the bore S8 is suitably tapered to receive thevalve head 92 when the valve 910. is in its uppermost posif tion, asshown, to prevent an upward ow of uid through the piston 84. An enlargedhead 9'4 is provided on the upper end ofL the valve 90 and is of adiameter to enter the upper extension 70 of the main chamber 72, as willbe more fully hereinafter set forth. The upper end 96 of the head 94engages the lower end of the push rod 46, when the head 94 enters thechamber extension 7 0 to raise the push rod 46. A suitable compressionspring 98 surrounds the valve rod 90 and is anchored between the head 94and the upper end of the piston 84 to yieldingly retain the valve Y901in its upper position, with the valve. head 92 in contact with thevalveseat at the lower end of the bore 88.

A tubular skirtr1r00 is provided on the 'lower end of the piston 84, totelescope over the reduced upper end 102 of a bottom plug member 104.The skirt 100 is preferably of a length to contact the upwardly facingshoulder 1 6 formed on the plug 10,4.at the lower end of the extension102, prior to the time the piston 84 will contact the upper endof theextension 102, whereby a space 108 is provided between the piston 84 andthe upper end of theY extension 102 when the piston is in its lowermostposition.

The.r lower vplug 104 is threadedly secured in the lower endof thehousing6,0, and is preferably sealed to the inner periphery ofthehousing 60 by a suitable sealing ring 110 to prevent the escape of liuidfrom the main chamber 72. A bore 112 extends vertically through thelower plug 104 to receive a charge 114 vof slow burning powder. Thepowder charge 114 is retained in the bore 112 by a-shoulder 116 at itsupper end and a second lower plug 118 at its lower end. Theplug 118 isthreaded into the lower end of the bore 112 and is preferably sealedtothe lower plug 104. A perforated retainer 120 is threadedly 'securedin the upper end of the vertical bore 112 a short distance above thepowder charge 114 to diffuse the gas evolved upon detonation of thecharge 114 as will be more fully hereinafter set forth.

A suitable detonator 122 is disposed in the upper end of the powdercharge 114 and is suitably grounded to the lower plug 104. The lead 56,extending from the switch 32, is directed through a passageway 124 inthe lower'por spaanse tion of the plug 104 and then upwardly through thecenter of the powder charge 114 to the detonator 122. The lead 56 will,of course, be insulated from the lower plug 104 and the powder charge114.

For clarity of description, all of that structure extending from theintermediate plug 4? downward will be designated by reference character126 and referred to herein as the perforating uid placement tool.

Operation Before running the perforating gun 16 and the attached huidplacement tool 126 in the well casing 12, the main chamber 72 of the uidplacement tool is filled with an optimum perforating uid, and the piston34 is positioned in the lower end of the chamber 72, with the skirt 166in contact with the shoulder 14196 of the lower plug 164. Theperforating uid placed in the chamber 72 may be any suitable type ofpetroleum oil, either relined or crude, which has a low huid loss. It ispreferred that the uid loss qualities of the perforating uid be lessthan 2 cc. when tested by the standard A.P.I. fluid loss test fordrilling fluids. lt is also preferred that the perforating uid have asuitable gelling agent, such as an alkali metal soap, incorporatedtherein, whereby the viscosity of the fluid will be substantial when theuid is at rest. ln any event, the perforating duid should have aviscosity greater than the viscosity of the drilling mud which is to bedisplaced from around the gun 16 in the casing 12. Also, the perforatingfluid should contain no solid material which cannot lbe washed olf theface of a formation by formation fluids entering the well. Fluids ofthis type are well known to the art of well completion.

Prior also to running the gun 16 in the casing 12, the switch 32 is setin such a position that the switch lever will be extended downwardly toplace the lead 36 in contact with the lead 56; and the push rod 46should be in its lowermost position with the upper head of the push rodin contact with the upper end of the intermediate plug member 40. Withthe perforating gun 16 and the fluid placement tool 126 assembled inthis manner, they may be run into the casing 12 on the lower end of thecable 18.

The method of this invention is best illustrated in FIG- URES 3 through6. As shown in FIGURE 3, the perforating gun 16, having the uidplacement tool 126 secured on the lower end thereof, is run into thewell casing 12 on the cable 18 until the perforating gun 16 is at thelevel where it is desired to perforate the casing 12. The current sourceat the surface of the well is then placed in operation to directelectric current downwardly through a lead in the cable 1S and the lead36 (FIGURE l) to the center pole of the switch 32. The current willproceed on downwardly through the lead 56 (FIGURE 2,) to the detonator122. Whereupon, the detonator 122 will be fired to ignite the powdercharge 114. As the powder charge 114 burns, gas will be forced upwardlythrough the perforated retainer 120 into the space 103 and against thelower face of the piston 84. The pressure of the generated gas will besutlicient to force the piston 84 upwardly through the chamber 72 todisplace the perforating luid from the chamber 72.

As the perforating fluid is forced upwardly, it lirst flows through thepassageway 70 and then outwardly through the ports 68 into contact withthe packer 76 and then upwardly through the ports 66, chamber 62, anddischarge ports 64. Since the discharging perforating fluid flowsthrough ports 64, the back pressure exerted by the perforating fluid inchamber 62 and ports 68 will be increased to such an extent that thepacker 76 will be expanded into sealing contact with the inner peripheryof the casing 12. This position of the packer 76 is illustrated inFIGURE 4.

The perforating fluid is forced on upwardly and out through thedischarge ports 64 into the annulus between the perforating gun 16 andthe well casing 12. The packer 76 prevents a downward flow of theperforating fluid; and since, the perforating uid has a higher viscositythan the drilling mud normally surrounding the perforating gun 16, theperforating iuid will displace the drill mud upwardly from around theperforating gun 16. A quantity of drill mud substantially equal to theperforating lluid displaced from the chamber 72 is allowed to ow fromthe well head (not shown). FIGURE 4 also illustrates the perforatinglluid being thus forced upwardly around the perforating gun 16 toeffectively displace all drilling mud from around the gun.

As the piston 84 (FIGURE 2) reaches the upper end of the chamber 72 andthe perforating fluid has been substantially discharged from the chamber72, the upper end 96 of the valve head 94 will contact the lower end ofthe push rod 4.6. Thus, flange stop 4S will fail in shear and the pushrod 46 will be raised to contact and throw the lever of the switch 32 toan upper position. When the switch 3.?, is thrown, the current from thelead 36 is directed to the detonator 2S for igniting the fuse 26 andtiring the shaped charges 24. The shaped charges 24 provide highvelocity jets which pierce the casing 12 as well as the cement sheath 14and enter the formation surrounding the well bore 1t). Such perforationsare illustrated by reference character 136 in FlGURE 5. It will beapparent that since the optimum perforating fluid surrounds the entireperforating gun 16 when the shaped charges 24 are fired, theperforations 13% will be lilled with the optimum perforating fluid, andthe low uid loss characteristics of the optimum perforating lluid limitsthe amount of the perforating fluid which will be lost to the formationthrough the perforations 13d. The perforating lluid also may contain anoil soluble plastering material which will lay a coat or blanket aroundthe inner periphery of the perfora-l tions tl, if desired.

Prior to the reversing or throwing of the switch 3-2, the upper end 96of valve 9? must Contact the lower end of push rod 46 causing it to moveupward. Push rod 46 under an upward load shears free from ange stop 4Sand moves upwardly with the same speed as valve 9i?. As the upperportion 9d of valve stem 90 enters recess 70 the reduced clearancebetween the head 94 and bore 76 results in a restriction in ow fromchamber 72 to ports 68. The flow area between head 94 and bore 70 isless than the combined flow area of ports 64. When this occurs, the rateof iluid ejection from chamber 72 is reduced and packer 7 6 begins toretract inwardly. Push rod 46 is forced upward and throws the toggle camof switch 32 upwardly, resulting in the switching of lead 36 (still hot)to detonator 23 which hres the shaped charges. The upper end 96 of valvestern 99 contacts the upper end of chamber 70 almost immediately afterdetonation of the perforating charges. When this occurs, valve stem 96isy restrained from further upward movement. Piston 84, still under theinfluence of expanding gas, continues to move upward causing the lowervalve head 92 to move olf its seat. Gas under pressure then flows pastvalve 912V; through relief passage 8d; thence etween upper end 94 andtherwalls of chamber 76, ports 65, ports 66, chamber 62, ports 64; andinto the annular space between the plug 46 and the cas-Y ing 12. Y

As indicated above, it is preferred that the packer 76 be retracted atleast a short distance prior to or simultaneous with the tiring of theperforating gun 16, whereby the greatly increased pressure around theperforating gun resulting from the tiring will not tend to injure orrupture the packer 76. lf the packer 76 is retracted substantiallysimultaneously with the firing of the perforating gun, the perforatingfluid surrounding the perforating gun will not have had an opportunityto be displaced by drilling mud, either from above or below the gun; andthe perforating fluid will be in the proper position for lling theperforations 136. The operation of retraction of the packer 76 andcreation of the perforations 13d is illustrated in FIG- After theperforating gun 16 is fired, the entire apparatus is removed from thewell casing 12 by raising the cable d 18. The packer 76 will have beencompletely deated and will not interfere with this removal operation.The removal of the perforating gun 16 and fluid placement toolA 126 isillustrated in FIGURE 6. After the apparatus has been removed from thewell, the perforating liuid remaining in the perforations .134) will begelled and will not be easily removed by circulation of the drilling mudin the casing 12. When the Well is subsequently placed on production,the formation fluids will ow through the perforations 134? into thecasing 12 and effectively wash the perforating iiuid from theperforations. in other wordsr the perforating uid will effectivelyprevent the entrance of drilling mud into the perforations, yet may beremoved from the perforations by the inward flow of for mation uids. Aspreviously indicated, if the perforating uid contains a plasteringagent, it should be oil soluble in order to be fairly rapidly dissolvedby formation uids, whereby the formation vfluids will readily flowthrough the perforations into the Well as soon as the well is placedY onproduction.

A modified perforating uid placement tooi is shown in FGURE 7 and isgenerally designated by reference character ,132. The tool 132 comprisesan upper plug 134 having external threads on its upper end forconnection with the lower end of a perforating tool 16 in a manner sirnilar to that previously described. The plug k134 has a push rod 136extending loosely therethrough to function in the same manner as thepush rod 46 described and shown in the embodiment of FIGURES 1 and 2.The lower end of the push rod 136 is positioned only a short distancebelow the plug'134 and preferably has a head 138 formed thereon. Aninsulated lead 149 also extends upwardly through the plug 134 forconnection with a single-pole, double-throw switch (not shown) in theperforating gun 16 in the same manner as previously described.

The lower end portion of the plug 134 is reduced in diameter andthreaded to receive the upper end 142 of a tubular housing 144. Thelower end of the housing 1144 is closed -by'a solid plug 146, wherebythe interior of the housing 144 defines an enlarged chamber 148.

A plurality of circumferentially spaced discharge ports 151? extendthrough the head portion :142 of the housing 144 to providecommunication between the chamber 148 and the outer periphery of thehousing. It is preferred that the discharge ports 151) extend upwardlyat an angle, whereby fluid forced outwardly through the ports will bedirected upwardly around the perforating gun 16. An inatable packer 152is secured around the outer periphery of the housing 144 immediatelybelow the discharge ports 150. 'The packer 152 is formed out of aresilient material and is of a size to engage the inner periphery of awell casing lor well bore when in an expanded position. A plurality ofports 154 extend through the walls of the housing 144 opposite thepacker152 to provide communication between the chamber 148 and the innersurface of the packer. It is preferred that a large number of the ports154 be provided, whereby pressure imposed on iiuid in the chamber 148will be effectively transmitted to the packer 152.

A plurality of relief ports 156 extend transversely through the wall ofthe housing 144 immediately below the packer 152 for purposes which willbe hereinafter set forth. The relief ports 156 are normally covered by asleeve -8 having a pair of spaced sealing rings 16) around the outerperiphery thereof in sealing engagement with the inner periphery of thehousing 144. The sealing rings 160 are spaced apart a sufficientdistance to straddle the relief ports 156 and effectively prevent theleakage of fluid from the chamber 148 through the relief ports 156 whenthe sleeve l158 is in the position shown in FIGURE 7. The sleeve 158 isheld in its normal position over the relief ports 156 by means of ashear plug 162 threadedly secured in the wall of the housing 144. Aspider 164 extends inwardly and Vupwardly from the sleeve 158 to supporta tripping bar 166. The tripping bar 166 Ahas a plurality ofcircumferentially spaced guides 168 on the upper end por'- tion thereofto retain the bar in the central portion of the chamber 148. The guides168 lmerely slide along the inner periphery of the housing 144 when thebar 166 is raised or lowered. The bar 166 -is utilized to contact thehead 138 of the push rod 136 and raise the push rod for actuation of theperforating gun 16, .as will be more fully `hereinafter set forth.

A piston 170 is slidingly disposed in the chamber 148 .below the sleeve158. The piston 17@ is sealed to the inner periphery of the housing 144by a `suitable sealing ring 172 and has a skirt 174 extending downwardlytherefrom. A plurality of ports 176 extend transversely through thepiston skirt. 174 for purposes which will be hereinafter set forth. Thelead S140, previously described as extending through the plug 134,extends on downwardly through the chamber :148 and then through thepiston 170 vby means of an insulated rod 178. The lower end oftheconductor rod 178 is inserted in a suitable electrical conhector 189carried in an extension 182 of the lower plug 146. The connector 186 isin turn connected to a suitable detonator 184 carried in the extension182 below the connector 181i.

A bore 186 extends downwardly into the lower plug `146 'of the plug 146near the upper end of the bore 186 to discharge gases resulting fromburning of the charge 188. The ports 190 communicate with the chamber148 below the piston `17th, whereby gases evolved from the powder charge188 will tend to raise the piston 170 in the chamber 148.

Before running the perforating iiuid placement tool 132 in a well, thepiston 170 is placed in its lowermost position, as shown in FIGURE 7,with the conductor rod 178 in engagement with the electrical connector180. The chamber 148 is -iilled with an optimum perforating uid of thetype previously described, and the switch ofthe perforating gun 16 ispositioned such that current supplied to the supporting cable of theperforating gun will be directed downwardly to land through the lead140. VThe perforating gun 16 and uid placement tool 132 are then runinto a Well bore in the same manner as previously described. vWhencurrent is supplied to the perforating gun, it flows through the lead140, the conducting rod 178, and connector v to the detonator 184. Uponfiring of the detonator 134, the powder charge 188 will be ignited `andgas will be evolved under high pressure through the ports 190 to act onthe lower face of the piston 170.

As the piston 170 is forced upwardly through the chamber l148, theperforating fluid will be displaced from the chamber through thedischarge ports 150. Simultaneously, the increased pressure of theperforating fluid will be transmitted through the ports 154 to expandthe packer 152 into engagement with the surrounding casing or well bore.As the piston 170 reaches the upper end of its stroke, it contacts thelower end of the sleeve 158 and ruptures the shear plug 162, whereby thesleeve 1'58 will be raised simultaneously upon further upward movementof the piston 170. The rod or bar 166 will be raised with the sleeve 158into contact with the head 138 of the push rod, 136. Thus, the switch ofthe perforating gun 16 will be thrown to fire the gun and perforate thecasing and formation surrounding the well bore, While the perforatingfluid surrounds the perforating gun. The perforating fluid dischargedthrough the ports 150 Will be directed upwardly by the packer 15'2 todisplace drilling mud from around the perforating gun 16 in the samemanner as previously described. Y

Substantially simultaneously with the tiring of the perforating gun 16,the lower sealing ring 160 of the sleeve 158 is raised above the reliefports 156. Whereupon. vtheY aoeftffs chamber 14S is placed intocommunication with the well bore below the packer 152 through the reliefports 156 land ports 176 in piston 170. Thus, the pressure imposed onthe opposite side of the packer 152 will be balanced; and the packerwill tend to retract out of engagement with the inner periphery of thecasing or well bore. Then the high pressures created by tiring theperforating gun 16 will not rupture or injure the packer 152. l

Subsequent to the perforation of the well, the perforating gun 16 andperforating uid placement tool 132 are removed from the well in the samemanner as previously described.

Another modified perforating fluid placement tool is partially shown inFIGURE 8 and is generally designated by reference character 200. Thetool 200 resembles the previously described tool 132 (FIGURE 7), inhaving the tubular housing 144 and piston 170 reciprocally disposed inthe housing 144. The piston 170 carries the conductor rod 178 forconnection at its upper end with the lead 140 and at its lower end tothe connector 180 in the same manner as previously described. Allportions of the perforating tool 200 in and connected with the upper endportion of the housing 144 are the same as described in connection withFEGURE 7.

The tool 200 diners from the previously described tool 132 in having anintermediate plug 202 threadedly secured in the lower end of the housing144. An extension 204 is threadedly secured on the upper end of theintermediate plug 202 and is of a diameter to extend upwardly into theskirt 174 of the piston 170. The extension 204 is also utilized tosupport the connector 180. A detonator 206 is secured in the upper endof the plug 202 below the connector 180, and a suitable shaped chargel208 is disposed immediately below the detonator 206 in such `a positionyto be red when the detonator 206 is ignited. A plurality ofcircumferentially spaced passageways 210 extends vertically through theplug 202 to provide communication between the chamber 148 and acounterbore 211 in the plug 202 immediately below the charge 203, forpurposes which will be hereinafter set forth.

A tubular extension 212 is threadedly secured in the lower end of theintermediate plug 202 and extends upwardly into the counterbore 211 ofthe plug 202 to a position adjacent the shaped charge 208. The upper endportion of the cylinder 212 is reduced in diameter and externallythreaded to receive an expendable cap member 214. The cap 214 ispositioned immediately below and in line with the shaped charge 20S. Theexpendable cap 214 is sealed to the upper end of the cylinder 212 andcloses off the upper end of a passageway 216 extending upwardly from theinner chamber 218 of the cylinder 212. it will also be observed that thecounter bore 211 in the lower end of the plug 202 is of a largerdiameter than the cap 214, whereby the upper end of the cap 214 is incommunication with the vertical passageways 210.

`A lling head 220v is threadedly secured in the lower end of thecylinder 212 and is sealed to the inner periphery of the cylinder bysealing rings 222 to effectively close oi the lower ends of the chamber218. A passageway 224 extends vertically through the central portion ofthe head 220 and has a stop valve 226 interposed in the lower endthereof. The stop valve 226 is operated by a suitable hand wheel 228mounted on the lower end of the valve operating rod 230. The rod 230extends through a suitable packing gland 232 secured in the lower end ofthe head 220. A gas-charging valve 234 of any Asuitable design issecured in the side of the lower end portion of the head 220 incommunication with the passageway 224 below the stop valve 226, wherebythe chamber 218 may be charged with gas when the stop valve 226 is open.A suitable cap 236 is threadedly secured on the head 220 to protect thehand wheel 228 and gas-charging valve 234 when the tool is run in a wellbore.

In preparing the tool 200 for use in a well, the cap 236 is removed andthe stop valve 226 is opened. A suitable 10 supply of high-pressure gas,such as helium or nitrogen, is then fed through the charging valve 234and passageway 224 into the chamber 218. Any high-pressure gas may beutilized, although it is preferred that the gas be inert in order thatit will not form an explosive mixture in the Well. The gas is injectedinto the chamber 213 until the pressure of the gas substantially exceedsthat which is required to raise the piston against the hydrostatic headof the drill mud in the well. The stop valve 226 and charging valve 234are then closed and the cap 236 is reassembled on the lling head 220.The chamber 148 of the housing 144 is filled with an optimum perforatinglluid in the same manner as previously described.

When current is passed through the lead 140, conductor rod 178 andconnector 180 to the detonator 206, the detonator will be red to igniteor fire the shaped charge 208. The high velocity jet created by theshaped charge 208 will pierce the expendable cap 214 directly above thevertical passageway 216 in the upper head portion of the cylinder 212.When this occurs, the high-pressure gas from the chamber 218 will bedischarged through the passageway 216, chamber 211, and passageways 210to act on the lower face of the piston 170. Whereupon, the piston 170will be raised in the chamber 148 to displace the perforating fluidupwardly in the same manner as previously described. l

The reduced pasageways 210 and the reduced passageway provided by thechamber 211 are utilized to throttle the high-pressure gas dischargingfrom the chamber 218, whereby a sudden pressure will not be imposed onthe lower face of the piston 170 and cause damage. It will be apparentthat the chamber 218 must be of substantial length to contain asuflicient supply of gas for raising the piston 170 in the chamber 148;however this is nota limiting factor on the use of such a tool, sincethe tool may be made of any suitable length without interfering with theperforating operation.

Another modied perforating uid placement apparatus shown in FIGURE 9 isgenerally designated by reference character 290 which encompasses all ofthe structure extending downwardly from the perforating means such as astring of charges 24 within tubular housing 22 of gun 16.

Placement tool 290 comprises an upper plug 246 having external threadson its upper end for connection to the lower end of perforating gun 16in a manner similar to that previously described. Plug 246 isconcentrically counterboredin order that a bore 250 partially extends lvertically through the central portion of the plug to receive a charge252 as a source of energy, such as a slow burning powder or a compressedgas.

Plug 246 is adapted to receive a charge retaining means 266 in anotherconcentric counterbore, and is internally threaded therein to receive aplug 270. Charge 252 is maintained in position by charge retaining means266 having shoulders 260, sealing means 258 and a bore 262 adapted toreceive a ilanged plug 268 having sealing means 264. A separate bore 244extends completely through plug 246 in a vertical manner to receive asuitable insulation means 248 and a lead wire 242.

The lead wire 242 depends from a switching means 238 in the lowerportion of perforating gun 16 lwhich is secured to housing 22 asdescribed above. (See FIGUREl l.) Switching means 238 is a switch havinga lirst and a second position, such as a multiple terminal steppingswitch.l A lead wire 36 extends upwardly from a pole of the switch tocable 18 and thence to the surface of the well whereby switch 238 isenergized when suitable electrical current is supplied from a surfaceinstallation (not shown).

Switch 238 is electrically connected in a lirst position to a detonator254 by wire 242 which passes through bore 244. enabling the detonator tobe energized by an operator at the surface. Detonator 254 is connectedby a ground wire 256 to charge retaining means 266 to assure a comgases.

1 l plete circuit. Switch 238 is connected by a suitable ground lwire240 to plug 246 and electrically connected in a second position to adetonator 28 which is in turn connected to fuseV 26 as disclosedhereinbefore.

Detonator 25'4 is in communication with charge 252 and capable ofigniting it to combust with rapidity to produce Charge retaining means266 keeps the charge in place and plug 268 prevents undesirable fluidsfrom contacting the charge. Means 266 is maintained in position by aplug 270 which is partially counterbored at the upper end to provide abore 272 in the upper portion and is externally threaded at both ends toattach to plug 246 and a housing 288. Plug 270 is also counterbored atthe lower end to provide a partial vertical bore or chamber 282 andcomplete vertical bores 274 as a series of passageways or verticalports. Plug 270 is further concentrically counterbored from the lowerend to provide a bore 278 which is adapted to receive transfer means.

The gases which expand into bore chamber 272 can communicate into theseries of pasageways 274 vertically through plug 270 which is attachedat the lower end by threaded means to housing 288. A suitable packingmeans v280' is attached to plug 270 which is laterally bored in thelower portion to provide a series of ports 284. Gases can communicatethrough passageways 274 into chamber' 282, within plug 270 and housing288, and through ports 284, thereby causing packing means 289 to beexpanded outwardly into the annular space between the apparatus 290 andthe well casing or bore. Chamber 282 is capable of containingperforating uid which also communicates with a transfer tube 286. Theupper end of transfer tube 286 is connected to the adaptable portion ofbore -278 within plug 270 which also contains a series of dischargeports 276 extending laterally in an outward and slightly upward mannerthrough plug 270.

Housing 288 has an aperture 292 at the lower end wherein a plug 294 isinserted in 292 and maintained in position by a shear pin 298. Sealingmeans 296 maintain the chamber 282 in a sealed condition during thedisplacement of Ythe perforation fluid from chamber through transfertube 286 and into the well bore. Excess pressure in chamber 282 due toplugging of a passageway, port or such will cause pin 298 to be shearedreleasing plug 294 thereby conserving the tool.

The Vdisplacement of the desirable perforating fluid into the well boreis as indicated above and especially in FIGURES 3-6 of the drawing.

Before lowering the perforating iiuid placement tool 290 into a well,the chamber 282 is filled with an optimum perforating iiuid of the typehereinbefore described.

The uid can be iilled directly into the upper end of housing 288 priorto threading the housing and plug 270 Y together, o-r it can be injectedinto apperture 292 after the apparatus is completely assembled,whereafter plug 294 is properly inserted. Powder charge 252 is insertedt into bore 250 and detonator 254 is atl'ixed to the charge andconnected to switching means V238 in the tirst position by wire 242.Charge retaining means 266 is then inserted into bore y272 with theflanged plug l268 properly -sealed in place, whereafter plug 270 isattached to plug 246 by threaded means and the filled Ychamber 282 isattached to plug 270 by threaded means.

The tool is then lowered into a Well and positioned by cable meanspreviously described to the desired position. Electrical energy 4istransmitted through cable 18 and lead wire 36 to switching means 238 inits iirst position so connection is complete to detonator 254 whichignites powder charge 252, Whereafter switching means 238 assumes thesecond position. Expanding gases from charge 252 displace flanged plug268 from the charge retaining means 266 and pass through bore 272 andthe series of passageways 274 into chamber 282. Gaseous pressure withinchamber 282 causes the perforating lluid to be diverted through ports284 causing'packing means I 280. 'Ilhis causes the fluid from chamber282 to displace Y l2 280 to be expanded to seal the annular space withinthe well casing or bore below the perforation gun.

As gases continue to fill chamber 282 the perforating uid is movedupwardly in transfer tube 286 to the bore 278 where it passes through'the series of discharge ports 276 outwardly and upwardly into theannular space snrrounding the perforating device above the packing meansthe undesirable iluids from the annulus about the peforation gun 16upwardly in such a manner that the gun is completely encased in thedesirable iiuid.

Thereafter, switching means 238, in its second position, is energizedand the detonator 28 is actuated which i in turn ignites fuse 26 andcauses the charges 24 to be activated. Thus the well casing isperforated in the presence of the optimum fluid and the gun andplacement tool are removed from the well bore as previously described.

From the foregoing, it will be apparent that the present inventionprovides a novel method nad apparatus for completing oil and gas wellswherein the maximum production obtainable through a perforatingoperation will be attained. It will also be apparent that the objectivesset forth in the forepart hereof are obtained.

Changes may be made in the combination and arrangement of parts orelements and steps as heretofore set forth in the specification andshown in the drawings withv out departing from the spirit and scope ofthe invention as set forth in the following claims.

I claim:

1. An attachment for a gun used in perforating wells, comprising ahousing attachable to the Vlower end of the gun, said housing having acylindrical chamber therein and a plurality of circnmferentially spacedoutlet ports at the upper end of the chamber, a piston reciprocallydisposed in the chamber, an energy source in the housing arranged toraise the piston through the chamber, a hydraulically actuated packer onthe housing below said outlet ports in communication with the chamber,and a rtiring mechanism Afor the gun in the housing arranged to beactuated by the piston as the piston reaches the upper end of thechamber.

' 2. An attachment as dened in claim lv characterized further in thatthe energy source comprises a slow burning explosive.

3. An attachment as defined in claim Vl characterized further in thatthe energy source comprises a compressed gas.

Y 4. An apparatus for perforating a casing or the like filled with acontaminated fluid, comprising an elongated housing, said housing havinga chamber therein for containing ,a supply of perforating fluid, saidhousing also having a plurality of circumferentially spaced outlets atthe upper end of said chamber for the dischargecof the perforatingliuid, a plurality of explosive actuated perforators carried in thehousing above said chamber, Va

hydraulically expandable packer carried by the housing in communicationwith said chamber and below said outlets, a piston reciprocally disposedin said chamber, an energy source in the housing below said piston formoving the piston upwardly through said chamber to eX- pand the packerand displace the contaminated uid from around the perforators withperforating fluid, and tiring means in the housing arranged to beactuated by said piston as said piston reaches the upper end of saidchamber for tiring said perforators subsequent to displacement of thecontaminated liuid from around said perforators.

5. An attachment -for a gun used in perforating wells, Y

ports and the lower end of Vsaid chamber, an energy source mounted inthe housing above and in communication with said chamber being arrangedto displace said iiuid from said chamber through said transfer tube, aswitching means for activating said energy source communicatingtherewith, and a hydraulically actuated packer mounted on the housingbelow said outlet ports in communication with the chamber.

6. An attachment as dened in claim 5 characterized `further in that theenergy source comprises a slow burning explosive.

7. An attachment as defined in claim 5 characterized further in that theenergy source comprises a compressed gas.

8. An apparatus `for perforating a casing or the like liilled with acontaminated fluid, comprising an elongated housing, said housing havinga chamber therein for containing a supply of perforating fluid, saidhousing also having a plurality of circumferentially spaced outletsabove said chamber for the discharge of the perforating fluid, aplurality of explosive actuated perforators carried in the housing abovesaid chamber, a hydraulically expandable packer carried by the housingin communication with said chamber and below said outlets, a transfertube iixedly disposed in the upper end of said chamber in communicationwith said outlet ports and the lower end of said chamber, an energysource mounted in the housing above and communicating with saidchairber, thusly said source communicates with said chamber, saidpacking means, the lower end of said tube, and said outlet ports, andswitching means mounted in the housing communicating with and adapted tosuccessively actuate the energy source and the perforators.

References Cited in the iile of this patent UNITED STATES PATENTS2,100,807 Kinley Nov. 30, 1937 2,569,893 Kendall et al. Oct. 2, 19512,693,856 Allen Nov. 9, 1954 2,696,259 Greene Dec. 7, 1954 2,715,943True Aug. 23, 1955 2,745,495 Taylor May 15, 1956 2,766,828 Rachford Oct.16, 1956

